We propose to organize a conference to discuss the structure and function of a fibroblast surface protein, which has several interesting properties. This protein is a major cell-type specific antigenic component of the normal fibroblast surface and is also found in the blood and in connective tissue matrix. It is a high molecular weight glycoprotein. The most striking characteristic of this protein is that it is lost from the cell surface upon malignant transformation. Recent evidence indicates that it may play an important role in regulating the adhesion, growth and attachment of cells, and in formation and maturation of tissue matrices in the final stage of blood coagulation. The plasma form of this protein has been known for a long time and has been rather well characterized. Its presence in fibroblasts and its sensitivity to transformation was first discovered about four years ago. Since then there has been a vast amount of work done on it and further interesting properties have been uncovered. The proposed conference would be the first one held to discuss these results. In the program we have made a special attempt to bring together investigators working on the various aspects of this and related proteins. Such an inter-disciplinary approach seems especially timely with regard to this protein because of the variety of biologically interesting systems it seems to be involved in. We expect the input from other fields in this meeting to further understanding of the cell structure alterations occurring upon malignant transformation and their significance to the growth control of the cell and vice-versa.